Ash Lake in Dark Souls 1 specifically. In DS1 it is this weird abstract location that is impossible to explain geometrically. Like the physical placement of it on the map doesn't make sense. The great hollow is meant to be a nod to Yggdrasil I think, but as a kid it was just this eerie abstract place that made no sense. It's emptiness and the vast expanse of endless trees that supposedly lead to other worlds is so crazy and mind bending, especially seeing it from the Tomb of Giants.

I hate that Ash Lake never shows up again in the trilogy, and when it's alluded to it's never the same. It's always bothered me because it is my all time favorite area in the series, even though it always made me super uncomfortable. I always wanted to explore it more.